Fuel control apparatus for gas turbine engines

ABSTRACT

A fuel control apparatus for a gas turbine engine comprises a metering orifice and a closure member for the orifice. The closure member is movable in response to engine speed and pressure signal from the engine compressor. The pressure signal is modified by a device sensitive to engine temperature. At engine temperatures above a predetermined level the device also modifies the position of the closure member directly and in a sense opposite to that applied by the modification of the pressure signal.

[ July 17, 1973 Primary ExaminerClarence RqGordon Att0rneyl-lolman &Stern [57] ABSTRACT A fuel control apparatus for a gas turbine enginecomprises a metering orifice and a closure member for the orifice. Theclosure member is movable in response to engine speed and pressuresignal from the engine compressor. The pressure signal is modified by adevice sensitive to engine temperature. At engine temperatures above apredetermined level the device also modifies the position of the closuremember directly and in a sense opposite to that applied by themodification of the pressure signal.

13 Claims, 1 Drawing Figure United States Patent Bloom FUEL CONTROLAPPARATUS FOR GAS TURBINE ENGINES [75] Inventor: Joseph Lewis Bloom,Droitwich,

England [73] Assignee: Joseph Lucas (Tndustries) Limited,

Birmingham, England [22] Filed: Sept. 23, 1971 211 Appl No.: 183,058

[52] U.S. CL... 60/3918 T [51] Int. Cl. F02c 9/10 [58] Field ofSearch..................... 60/3928 T, 3928 [56] References Cited UNITEDSTATES PATENTS enew/4 u A 0 u PAIENIE JUL 1 7 I975- lllll INVENTOR Mme i[earl/178M.

FUEL CONTROL APPARATUS FOR GAS TURBINE ENGINES This invention relates toa fuel control apparatus for a gas turbine engine and has as an objectto provide such an apparatus in a convenient form.

According to the invention a fuel control apparatus for a gas turbineengine comprises a fuel metering orifice, a control element operable tovary the effective area of the orifice in accordance with increases indesired and actual engine speeds respectively to increase and decreasefuel flow and in accordance with increase in an air pressure signalderived, in use, from the engine compressor to increase fuel flow, adevice responsive to the temperature at a desired location on theengine,

valve means actuable by the device to increase the value of the said airpressure signal with increase in the said temperature and a linkageoperable by the device with increases in the said temperature above apredetermined level to urge the control element to reduce fuel flow.

An example of fuel control apparatus according to the invention will nowbe described with reference to the accompanying drawing which shows suchan apparatus diagrammatically.

A casing has an inlet 11 and an outlet 12. Between the inlet 11 andoutlet 12 is an orifice 13 whose effective area is controlled by aclosure member 14 formed to present an L-shapedmetering edge to theorifice 13. The closure member 14 is rotatable about a pivot 15 so thatclockwise movement of closure member 14, as shown in the drawingoperates to reduce the effective area of orifice l3. Pivot 15 is itselfmounted on a spindle l6 rotatable within the casing 10 by a lever 17coupled to a bellows l8. Bellows 18 is situated in a sealed chamber 19within the casing 10. Rotation of spindle 16 in an anticlockwisedirection, viewed on arrow A, also operates to reduce the effective areaof orifice 13. Limits of movement of the closure member 14 about thepivot 15 are defined by adjustable stops 20, 21.

Limits of movement of the spindle 16 are likewise defined by adjustablestops 22, 23.

The closure member 14 is engaged by a governor mechanism 24 driven, inuse, by the associated engine and operable in response to an increase inengine speed to urge the closure member 14 to reduce the effective areaof the orifice l3. Closure member is biased against the action ofgovernor mechanism 24 by a spring 25. The force applied by spring 25 isvariable by a lever member 26 pivotally mounted in the casing 10 andengaging an abutment 27 which is, in turn, pivotally mounted. on aplunger 28 slidable in the casing 10. Abutment 27 is also engaged by apush rod 29 which forms the follower for a cam 30 rotatable by theengine throttle control. The abutment 27 is biased into contact withlever member 26 and a rod 29 by a spring 31 engaging the plunger 28. Thelimits of travel of the lever member 26 are defined by a pair ofadjustable stops 32, 33.

In series with the orifice 13 is a pressurising valve 34 biased by aspring 35 and having a stem 36 engageable with the cam 30. Apositive-displacement pump 37 has an inlet 38 communicating, via a boostpump 39, with a fuel tank (not shown). Pump 37 has an outlet 40communicating with the inlet 1 1 of the control arrangement. A spillvalve 41 is connected to the inlet 38 and outlet 40 of the pump 37 viapassages 42, 43 respectively. Valve 41 has a closure member 44responsive to the pressure drop across the orifice 13 and biased againstthe said pressure drop by a spring 45.

A device 47 responsive to the temperature in the engine compressorintake includes a temperaturesensitive element 47 having a stem 48extending therefrom, stem 48 being movable downwardly, as shown, inresponse to an increase in the temperature sensed by the element 47.Stem 48 is biased against the said downward movement by a spring 49.Stem 48 passes through a chamber 50 having an inlet 51,. an outlet 52communicating with the chamber 19 in the casing 10, and a restrictedoutlet 53. The stem 48 forms a variable flow restrictor between theinlet 51 and the outlets 52, 53. The device 46 also includes a plunger54 engageable with the stem 48 and linked via a flexible cable 55 with afurther plunger 56 within the casing 10. Plunger 56 abuts plunger 28 andis thus operable by stem 48 to displace plunger 28. A flange 540 onplunger 54 acts to limit the movement thereof under the influence ofspring 31.

In use, fuel supplied by the pump 34 passes via inlet 11 to the orifice13. Closure member 14 is rotated about pivot 15 to an equilibriumposition in which the force exerted on member 14 by the governormechanism 24 is balanced by the force exerted by the spring 25. Thestiffness of spring 31 is substantially greater than that of spring 25.Plunger 28 thus adopts a position in which it abuts plunger 56, urgingplunger 54 to the limit of travel imposed either by flange 540 or byengagement with stem 48. The air pressure at the delivery of the enginecompressor is supplied to the inlet 51 of device 46. The variable flowrestrictor formed by the stem 48 combines with the restricted outlet 53to provide an air potentiometer. An air pressure signal intermediateambient and compressor delivery pressure is thus applied, via outlet 52to the chamber 19. The pressure in chamber 19 acts on the outside of thebellows 18 to rotate the spindle 16, an increase in the air pressuresignal operating to increase the effective area of orifice 13. Theeffective area of orifice 13 is thus variable in accordance with enginespeed, throttle setting, compressor delivery pressure and compressorintake temperature.

Reduction in the area of orifice 13 results in an increase in pressureupstream thereof. This pressure is applied via passage 43 to one side ofclosure member 44 of spill valve 41. The pressure downstream of orifice13 is applied to the other side of closure member 41. The saiddownstream pressure is maintained substantially constant by thepressurising valve 34. Valve 41 is thus sensitive to a pressure dropacross orifice 13 to spill excess fuel back to the inlet 38 of pump 37.In the shut-off position of the engine throttle, cam 30 engages stem 36to operate valve'34 as a shut-off valve.

If the compressor intake temperature rises sufficiently to cause thestem 48 to engage and move the plunger 54, this movement causes plunger56 to urge plunger 28 against the spring 31. The abutment 29 thus pivotsabout push-rod 29 and, via lever 26 and spring 25, permits closuremember 14 to move in a direction to reduce fuel flow.

Thus below a predetermined level, increase in temperature at thecompressor intake results in an increase in pressure in chamber 19 andhence an increase in fuel flow to the engine. An increase in temperatureabove this predetermined level urges the closure member 14 to reducefuel flow to the engine.

I claim:

1. A fuel control apparatus for a gas turbine engine, comprising a fuelmetering orifice, a control element operable to vary the effective areaof the orifice in accordance with increases in desired and actual enginespeeds respectively to increase and decrease fuel flow and in accordancewith increase in an air pressure signal derived, in use, from the enginecompressor to increase fuel flow, a device responsive to the temperatureat a desired location on the engine, valve means actuable by the deviceto increase the value of the said air pressure signal with increase inthe said temperature and a linkage operable by the device with increasesin the said temperature above a predetermined level to urge the controlelement to reduce fuel flow.

2. A fuel control apparatus for a gas turbine engine, comprising a fuelmetering orifice, a control element operable to vary the effective areaof the orifice in accordance with increases in desired and actual enginespeeds respectively to increase and decrease fuel flow and in accordancewith increase in an air pressure signal derived, in use, from the enginecompressor to increase fuel flow, a device responsive to the temperatureat a desired location on the engine, valve means actuable by the deviceto increase the value of the said air pressure signal with increase inthe said temperature, a linkage operable by the device with increases inthe said temperature above a predetermined level to urge the controlelement to reduce fuel flow, and a govenor mechanism responsive to thespeed of the engine, the control element being mounted for movementabout a first axis by the govenor mechanism.

3. An apparatus as claimed in claim 2 which includes an elementresponsive to the said air pressure signal, and the control element ismounted for pivotal movement about a second axis by the pressureresponsive element.

4. An apparatus as claimed in claim 3 in which the first and second axesare substantially mutally perpendicular.

5. An apparatus as claimed in claim 3 in which the pressure responsiveelement is a bellows.

6. An apparatus as claimed in claim 2 which includes a spring engagingthe control element and biasing the latter against movement by thegovernor mechanism in response to an increase in engine speed.

7. An apparatus as claimed in claim 6 which includes a lever supportingthe end of the spring remote from the control element and pivotallymovable by temperature responsive device when the temperature is abovesaid predetermined level to vary the bias applied by the spring.

8. An apparatus as claimed in cliam 7 which includes means responsive tothe position of a throttle control for the engine to pivotally move thesaid lever.

9. An apparatus as claimed in claim 7 in which the temperatureresponsive device includes a stem which forms a control member for saidvalve means.

10. An apparatus as claimed in claim 9 which includes a fluid flowrestrictor which combines with said valve means to form an airpotentiometer, the said air pressure signal being that between the saidvalve and restrictor.

11. An apparatus as claimed in claim 10 which includes a plunger movableby said stem at temperatures above said predetermined level, and meansinterengaging said plunger and said lever.

12. An apparatus as claimed in claim 1 l in which said interengagingmeans comprises a further lever pivotally mounted about an axis which ismovable by said plunger, said further lever being pivotally movableabout its axis by said means responsive to the engine throttle control,and being engaged by the first mentioned lever.

13. An apparatus as claimed in claim 12 in which said interengagingmeans further comprises a further plunger abutting said further leverand a flexible cable connecting the said plungers.

t t i

1. A fuel control apparatus for a gas turbine engine, comprising a fuelmetering orifice, a control element operable to vary the effective areaof the orifice in accordance with increases in desired and actuAl enginespeeds respectively to increase and decrease fuel flow and in accordancewith increase in an air pressure signal derived, in use, from the enginecompressor to increase fuel flow, a device responsive to the temperatureat a desired location on the engine, valve means actuable by the deviceto increase the value of the said air pressure signal with increase inthe said temperature and a linkage operable by the device with increasesin the said temperature above a predetermined level to urge the controlelement to reduce fuel flow.
 2. A fuel control apparatus for a gasturbine engine, comprising a fuel metering orifice, a control elementoperable to vary the effective area of the orifice in accordance withincreases in desired and actual engine speeds respectively to increaseand decrease fuel flow and in accordance with increase in an airpressure signal derived, in use, from the engine compressor to increasefuel flow, a device responsive to the temperature at a desired locationon the engine, valve means actuable by the device to increase the valueof the said air pressure signal with increase in the said temperature, alinkage operable by the device with increases in the said temperatureabove a predetermined level to urge the control element to reduce fuelflow, and a govenor mechanism responsive to the speed of the engine, thecontrol element being mounted for movement about a first axis by thegovenor mechanism.
 3. An apparatus as claimed in claim 2 which includesan element responsive to the said air pressure signal, and the controlelement is mounted for pivotal movement about a second axis by thepressure responsive element.
 4. An apparatus as claimed in claim 3 inwhich the first and second axes are substantially mutally perpendicular.5. An apparatus as claimed in claim 3 in which the pressure responsiveelement is a bellows.
 6. An apparatus as claimed in claim 2 whichincludes a spring engaging the control element and biasing the latteragainst movement by the governor mechanism in response to an increase inengine speed.
 7. An apparatus as claimed in claim 6 which includes alever supporting the end of the spring remote from the control elementand pivotally movable by temperature responsive device when thetemperature is above said predetermined level to vary the bias appliedby the spring.
 8. An apparatus as claimed in cliam 7 which includesmeans responsive to the position of a throttle control for the engine topivotally move the said lever.
 9. An apparatus as claimed in claim 7 inwhich the temperature responsive device includes a stem which forms acontrol member for said valve means.
 10. An apparatus as claimed inclaim 9 which includes a fluid flow restrictor which combines with saidvalve means to form an air potentiometer, the said air pressure signalbeing that between the said valve and restrictor.
 11. An apparatus asclaimed in claim 10 which includes a plunger movable by said stem attemperatures above said predetermined level, and means interengagingsaid plunger and said lever.
 12. An apparatus as claimed in claim 11 inwhich said interengaging means comprises a further lever pivotallymounted about an axis which is movable by said plunger, said furtherlever being pivotally movable about its axis by said means responsive tothe engine throttle control, and being engaged by the first mentionedlever.
 13. An apparatus as claimed in claim 12 in which saidinterengaging means further comprises a further plunger abutting saidfurther lever and a flexible cable connecting the said plungers.